Great work. But, I wonder if is this is just a case of different browsers focusing on different metrics? Chrome seems to have shifted its focus on paint timing metrics [1], while Mozilla is optimizing load timing metrics.

Personally, I feel optimizing both metrics are important. It would be nice if this study had also published a comparison of paint timing metrics.

[1] https://developers.google.com/web/updates/2017/06/user-centr...